# CALCULATING STANDARD DEVIATION WORKSHEET

Find the mean and standard deviation from the bar graph given below.

Problem 1 :

Solution

Problem 2 :

Solution

Problem 3 :

Solution

Problem 4 :

Solution

Problem 5 :

Solution

1)  mean = 8 and standard deviation = 2

2)  mean = 8 and standard deviation = 1.16

3)  mean = 7 and standard deviation = 1.84

4)  Mean = 13 and standard deviation = 0.80

5)  Mean = 3.5 and standard deviation = 1.72

Problem 1 :

The weekly wages (in dollars) of 90 workers in a steel yard are given alongside :

Find estimates of the mean wage and the standard deviation of the wages.

 Wage (\$)360 - 369.99370 - 379.99380 - 389.99390 - 399.99400 - 409.99410 - 419.99420 - 429.99430 - 439.99 Number of Workers516271612842

Solution

Problem 2 :

A random sample of the weekly supermarket bills for a number of families was observed and recorded in the table given.

a. Find the mean bill and the standard deviation of the bills.

b. variance of the population

 Bill (\$)70 - 79.9980 - 89.9990 - 99.99100 - 109.99110 - 119.99120 - 129.99130 - 139.99140 - 149.99 No. of families273248253721187

Solution

Problem 3 :

The length of 30 randomly selected 12 day old babies were measured to the nearest cm and the following data obtained.

i) Find the mean length and standard deviation of the lengths.

ii) Find the variance.

Solution

1)  Mean wages = 392.10 and Standard deviation = 16.34

2)  Mean = 103.50, Standard deviation = 19.14

b)  Variance = 366.33

3)  i) Mean = 47.76, standard deviation = 2.65

ii) Variance = 7.05

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